US2370513A - Production of conjugated diolefins - Google Patents

Description

Patented Feb. 27, 1945 PRODUCTION OF CONJUGATED DIOLEFINS James L. Amos, Midland, and Frederick J. Soderqulst, Bay City, Mich, aslignors to The Dow Chemical Company, Midland, Mich., a

corporation oi Michigan No Drawing. Application February 28, 1942, Serial No. 432,825

11 Claim.

This invention relates to the production of conjugated dioieflns and more particularly to the formation of the same by the dehydrogenation of olefins containing four to five carbon atoms in the molecule.

It is known that certain olefins may be dehydrogenated in gaseous phase under the influence of heat and solid catalytic bodies. such as metal compounds, porous substances, etc., to form conjugated dioleflns. However, in previouslyknown processes for carrying out such dehydrogenation diiiiculty has been experienced due to low conversion of the olefin to diolefln with consequent low percentages of dioleflns in the effluent gas mixture, to the cracking o! the olefin to form relatively large amounts of compounds containing a smaller number of carbon atoms in the molecule and to the rapid deposition of carbon on the catalyst body employed, thus rendering the latter inefiective after a short period of time.

We have found that alkenes having four to five carbon atoms in the molecule and having an unsaturated straight chain of at least four carbon atoms may be dehydrogenated readily, and with a high conversion during a single pass through the reaction zone, to form conjugated diolefins by pyrolyzing in the presence of water vapor and a hydrogen halide catalyst. We have further found that when the dehydrogenation is carried out in this manner, the use of the usual solid catalytic bodies, such as metal compounds, porous substances, etc., is unnecessary and, consequently. the necessity of frequently stopping the operation to clean or regenerate such solid catalyst is avoided. By using a hydrogen halide catalyst to promote the reaction, carbonization may be greatly reduced and the amount of cracking to form by-products having fewer carbon atoms in the molecule than the alkene reactant may be reduced below that usual when employing only solid catalysts in the reaction. An additional advantage resulting from the use 01' a hydrogen halide catalyst is that a crude diolefin fraction containing an exceptionally high proportion of diolefin may be recovered from the reacted mixture, thus greatly iaciiitating isolation of purified diolefln from the fraction.

The dehydrogenation is carried out in any suitable manner. e. g., by passing the alkene, water, and hydrogen halide catalyst in vapor phase through heated tubes. Although the process is preferably carried out in the absence of the usual solid catalytic bodies, it should be mentioned that such bodies may also be employed ii desired. In

some instances the use of such catalytic bodies will even lead to appreciably better yields of diolefin than when the solid catalytic body is omitted. Furthermore, the use oi water vapor and hydrogen halide in the reaction mixture decreases the deposition oi tree carbon on the catalytic body and increases the length of time over which the latter may be used without regeneration. However, the advantages gained by the use of such solid catalytic bodies do not usually justiiy the added expense and inconvenience involved.

The alkene, which may comprise i-butene, 2- butene, Z-methyl-l-butene, Z-methyl-Z-butene, 2-methyl-3-butene, l-pentene, or 2-pentene may arise in any of a number of ways, such as by a cracking operation, by dehydrogenation of a parafiln hydrocarbon. or by the elimination oi a hydrogen halide trom a haloparamn. Although the purity of the reaction product depends somewhat on the purity of the alkene used, the invention contemplates the use of the alkenes, or mixtures thereof, with at least minor proportions of other hydrocarbons, such as propane, butane, pentane, propene, isobutene, etc.

The hydrogen halide catalyst may be obtained from any convenient source, such as by the action of sulphuric acid on sodium chloride or as by-product hydrogen halide recovered from a halogenation reaction wherein a hydrogen halide is one of the products. Organic compounds such as monoor polyhalohydrocarbons, halohydrins, halocarboxylic acids, halo esters, etc, which are capable 0! being decomposed during the pyrolysis to form a hydrogen halide may also be used as a means oi introducing the hydrogen halide into the reaction mixture, and are herein included in the term hydrogen halide catalyst." In similar manner the term "hydrogen bromide catalyst," as used herein, includes hydrogen bromide and compounds which decompose during the pyrolysis to form hydrogen bromide. Among the halogen compounds which may be incorporated in the reaction mixture and which decompose during the pyrolysis to iurnis'n a hydrogen halide are ethylene chloride, ethyl bromide, propylene bromide, proply chloride, butyl bromide, butyl chloride, butyl iodide, butylene bromide, butylene chloride, amyl bromide, allyl bromide, ethylene bromohydrin, ethylene chlorchydrin. propylene chlorohydrin, chloroacetic acid, bromoacetic acid, ethyl. chloroacetate. ethyl bromoacetate, chloroethyl acetate, etc. The use of haloparaffins having the same number of carbon atoms in the molecule as the diolcfln being produced is particularly advantageous, since during the decomposition of the haloparaflin to produce a hydrogen halide, the desired conjugated diolefln is usually also formed. Mixtures of hydrogen halide catalysts may be used, if desired. When hydrogen chloride is used, its constant boiling mixture with water may be employed advanta' seously, since the use of such mixture simplifies the introduction of the acid and water in constant proportion into the reaction mixture. Furthermore, the constant boiling mixture may be condensed readily from the reacted mixture, if desired, and natively, the water may be introduced as steam into the reaction mixture.

The proportions of the reactants will, of

course, vary somewhat with the particular alkene be re-used in the process. Alterand hydrogen halide catalyst used and also with Llu: reaction conditions which are employed. Thus, under otherwise comparable conditions, hydriodic acid is more eflective than hydrobromic acid, which, in turn, is more eflective than hydrochloric acid. Less than one chemical equivalent, usually from 0.01 to 0.8 chemical equivalent of hydrogen halide catalyst is used for each moi of alkene. It should be mentioned that a chemically equivalent proportion oi hydrogen halide catalyst is considered herein as being equal to the molecular proportion of the same divided by the number of halogen atoms in the molecule. From 1 to 60 'mols, preferably i'roin to 45 mols, oiwater is used for each moi of alkenc, although larger proportions of water may be used, if desired. It is, of course. obvious that the use of excessive proportions of water may render the process less economical due to the larger amount of heat required to bring the mixture to the pyrolyzing temperature.

The reactants are usually preheated separately before being mixed together and subjected to the pyrolysis, although they may be heated after being mixed. if desired. The steam may be. advantageously superheated and mixed with the other ingredients to supply the heat of pyrolysis to the mixture. It should be mentioned that corrosion of the equipment used for handling the reactants may be greatly reduced by introducing the hydrogen halide catalyst in the form of a compound which decomposes in the reaction zone to liberate a hydrogen halide or, in case a hydrogen halide is used, by admixing it, preferably without preheating, with the other ingredients just prior to the entrance of the reaction mixtime into the reaction zone.

Although the reaction temperature depends somewhat upon the hydrogen halide catalyst used and the proportion thereof in the reaction mixture, [.18 dehydrogenation is usually carried out at temperatures between 600 and 950 C., preferably between 650 and 900 C. The time of pyrolysis is usually measured by the spacevelocity of the alkene within the reaction zone. The space velocity of the alkene may be defined us the number of cubic feet of gaseous alkene, r ferred to standard conditions of 0 C., and 760 mm. of mercury pressure, passing through the reaction zone per hour per cubic foot of reaction zone. It should be noted that the space velocity rs defined above refers to the alkene in the re action mixture and not to the reaction mixture as a whole. Thus, the space velocity of the aikene may be spoken of independently of the composition of the reaction mixture. The space velocity of the alkone is usually maintained between 200 and 600, and preferably between 250 and 500. Higher or lower space velocities may, of course, be maintained if desired. The dehydrogenation is usually carried out at atmospheric pressure, but higher or lower pressures may be used.

The use of the dioxides of sulfur and selenium in the pyrolysis mixture as disclosedin our copending application Serial No. 432,824 increases the effectiveness of the hydrogen halide catalyst in promoting the formation of the diolefin. Such oxide is usually used in an amount corresponding to between 0.01 and 0.6 me] for each mol of alkene. The sulphur dioxide may be introduced in gaseous phase, and the selenium dioxide may conveniently be dissolved in the water and the solution then heated and vaporizedlor atomized into the reaction zone. The sulphur and selenium dioxides are largely converted during thepyrolysis into hydrogen sulphide and hydrogen selenide. respectively.

After the pyrolysis. the reacted mixture=whlch.. comprises water vapor, a hydrogen :halide, lthet,

conjugated diolefln. i. e., 1.3-butadiene or a methylbutadiene, and any unconverted alkene together, usually, with minor amounts of Battle? rated and unsaturated hydrocarbons having a different number or carbon atoms in the. mole--: cule than the alkene used, may be treated'in any: of a number of ways to recover the conjugated:

diolefln formed during the pyrolysis. For example, the gaseous mixture may be cooled to I condense out an aqueous solution of the hydrogen halide which may either be discarded or returned to the pyrolysis stop. The uncondensed portion" may be scrubbed with water to remove any re maining traces of hydrogen halide. and ,the

washed gases then iractionally condensed to recover the unreacted alkene and the formed -dioleflnas a liquid fraction containing a highw concentration of the latter. The mixture. oi

alkene and diolefin may then be separated intoits components in known manner, e. 3.. by extraction with a selective solvent for the diolefln .or by reaction of the diolefln with a reagent such as cuprous chloride to form an insoluble complex salt, to recover substantially pure con- Jugated dlolefin and an alkene fraction which, may, if desired, be returned to the pyrolyzing.

step. In some instances the mixture of alkene and dlolefin may be used directly as a source of diolefln, e. g., in the preparation of sulphones.

of diolefins by selective reaction of the diolefln.

in the hydrocarbon mixture with sulphur dioxide. Hydrogen sulphide or hydrogen selenlde, ii

present in the reacted mixture are partially removed during the scrubbing with water, but are contained principally in the vent gases after separation of the fraction containing the alkene and diolefln. The vent gases may be discarded or, in case they contain the relatively valuable" selenium, they may, if desired, be burned to recover the latter as the dioxide which may be reused in the pyrolysis step.

The accompanying table shows the results of a number of experiments carried out at atmospheric pressure in each or which one moi oi the alkene listed was passed together with the noted amounts of steam and of the indicated hydrogen halide catalyst through a heated reaction chem her. The pyrolysis conditions, i. e., the spacevelocity of the alkene and the temperature. are A noted for each experiment together with the mole oi alkene recovered. the mole of conjugated" di- .i olefin formed, and the male 0! diolefln formed per mol allrene consumed. In the last column at a temperature in the range 600' to 900 C. and is listed the per cent diolefln in the recovered recovering a conjugated diolefln from the re- !raction containing the alkene and dlolefln prior acted mixture.

to separation into its components. 4. The method for preparing LB-butadiene Table Pyrolysis conditions MOI Moi Per cent Ex Moi H dro an M0 M01 can u Mad diolefln dlolelln N Alkene alkene all 0 mm t n m alkene a g formed per in alkenc- 0. used catalyst 75 B one Toma, recovered armed moi alkcne dlolefln vc oolty O. consumed Motion 1 1 None 380 775 0. 718 0. 081 0.191 7. 1 2 i ROI 0. l 10 87 i 775 0. 572 0. 1M 0. 248 16- 8 3--- 1 H51 1. 0 10 370 770 0. 042 0. 147 0. 411 I). 9 4. 1 H31 0. 1 10 B72 770 0. 380 0. 228 0. 373 80. 2 5. l KB! 0. l 10 375 825 0. 153 (it 83 0. ill. 0 0. 1 H31 0. 01 10 300 775 0. 497 0. 146 0. 288 I1. 0 7. 1 HI 0. 1 10 375 775 0. 605 0. 217 0. 00 26. 0 a... 1 Hi i 0.01 10 372 775 0. 008 0.100 0.303 21.2 0 l HBr i 0. l 10 350 825 0.155 0. 080 0. 46 08.0 10... l H131 0. l 10 B50 0. 28 0.860 0. 54 48.0 11... 1 BI'GBHIOH 0.1 10 372 800 0.288 0.320 0.45 60.0 12... l Cal-111B! 0.01 10 3']! (LI! 0.23 0.28 63.0 11L. Mixture oi l-hutene 1 1 HC] 0.9 16 7. 5 1 550 775 0. 405 0. 2 0. 411 34.0

and zbutene. MU, l 110] 0.92 7.5 350 750 0.52 0.207 0.505 H 31.2 15. Crude butane I 1.0 5.0 034 150 0. 34 0.20 0.30 no 10 .do. 1.0 Hiir 0.17 0.1 I 348 725 0. i1 0. 20 0.41 28.0 11. do. i 1.0 7.0 370 125 0.37 0.10 0.24 22.! iii... .110. 1.0 Illir 0.20 8.1 l 340 700 0. 31 0.28 0.45 38.2 liL. Crude )entcne 1.0 [Iiir 0.18 7. I 3 305 725 0. 123 0. 37 0. 41 06. 8 20..." do. l 1.0 as 200 125 0.54 0.17 can 204 Reaction mixture also con tained 0.05 mol sulphur dioxide.

1 Reaction chamber packec with 4-10 mesh pumice.

Reaction chamber packed with 4-8 mesh activated alumina.

' Reaction chamber packed with 4-8 mesh natural bauxite.

5 (proposition 0! crude buteiic: n-butene 81.87, iso-butcne 14.67 butane 2.5 combined high and low boiling fractions 1.1%. i Composition 0i crude pentcno: pcutenes 06.9 pentane 2.8%, high boiling raction 1.3%.

Other modes of applying the principle 0! our which consists in passing a gaseous mixture cominvention may be employed instead of those exprising a normal butene, water vapor, an oxide plained, change being made as regardsthe methselected from the class consisting of sulphur diod herein disclosed. provided the step or steps oxide and selenium dioxide, and a hydrogen halstated by any or the following claims or the ide catalyst through a reaction zone maintained equivalent of such stated step or steps be emat a temperature in the range 600 to950 C. ployed, 5. The method for preparing 1.3-butadiene We therefore particularly point out and diswhich consists in passing a gaseous mixture comtinctly claim as our invention: prising a normal butene. water vapor, an oxide 1. The method for preparing a conjugated diselected from the class consisting of sulphur diolefin which consists in passing a gaseous mixoxide and selenium dioxide, and a hydrogen halture comprising an alkene containing from four ide catalyst at a space velocity of 200 to 600 to flve carbon atoms in the molecule and having through a reaction zone maintained at a teman unsaturated straight chain of at least four peraturc in the range 600 to 950 0. carbon atoms, water vapor, an oxide selected 0. The method for preparing LB-butadiene from the class consisting of sulphur dioxide and which consists in passing a gaseous mixture comselenium dioxide, and a hydrogen halide catalyst prising one molecular proportion of a normal through a reaction zone maintained at a tembutene, from 1 to molecular proportions of perature in the range 600 to 950 C. water vapor, from 0.01 to 0.6 molecular propor- 2. The method for preparing a conjugated ditions of an oxide selected from the class consistolefin which consists in passing a gaseous mixing of sulphur dioxide and selenium dioxide and tore comprising an aikene containing from four from 0.01 to 0.8 chemically equivalent proportions to five carbon atoms in the molecule and having 01 a hydrogen halide catalyst at a space velocity an unsaturated straight chain of at least four or from 200 to 600 through a reaction zone maincarbon atoms, water vapor, an oxide selected tained at a temperature in the range 600 to from the class consisting of sulphur dioxide and 950' c. selenlm dioxide, and a hydrogen halide catalyst 7. The method for preparing 1.3 blitadiene at a space velocity of from 200 to 600 through a which consists in passing a gaseous mixture comreaction zone maintained at a temperature in 00 prising one molecular proportion 01' a normal the range 650 to 900 C. and recovering a conbutene, from 3 to 45 molecular proportions of jugated diolefln from the reacted mixture. water vapor. from 0.01 to 0.6 molecular propor- 3. The method for preparing a conjugated ditions of an oxide selected from the class consistolenn which consists in passing a gaseous mixing of sulphur dioxide and selenium dioxide and ture comprising one molecular proportion of an from 0.01 to 0.8 chemically equivalent proportions alkene containing from four to five carbon atoms of a hydrogen bromide catalyst at a space vein the molecule and having an unsaturated locity of from 250 to 500 through a reaction straight chain 0! at least iour carbon atoms. zone maintained at a temperature in the range from 3 to 45 molecular proportions of water va- 650 to 900 C. and recovering 1.3-butadiene por. from 0.01 to 0.6 molecular proportions of from the reacted mixture. an oxide selected from the class consisting of 1110- 8. The method for preparing l.3-buto.di phur dioxide and selenium dioxide, and from 0.01 which consists in passing a gaseous mixture comto 0.8 chemically equivalent proportions of a hyprising one molecular prgportlon of a normal drogen halide catalyst at a space velocity of from butene, from 3 to 45 molecular proportions of 200 to 600 through a reaction zone maintained 70 water vapor. from 0.01 to 0.8 molecular propor- 9. The method for preparing L3butadiene which consists in passing a gaseous mixture comprising one molecular proportion of a normal butene, from 8 to 45 molecular proportions of water vapor, sulphur dioxide and from 0.0l to 0.8 molecular proportions of hydrogen bromide at a. space velocity oi from 200 to 600 through a. reaction zone maintained at a temperature in the range 850 to 900 C.

10. The method for preparing LIi-butadiene which consists in passing a gaseous mixture comprising one moleculor proportion of a normal butene, from 3 to 45 molecular proportions of water vapor. from 0.01 to 0.6 molecular propornormal:

time oi sulphur dioxide and from 0.01 to 08 molecular proportions of hydrogen brqmldomtp space velocity or from 200 lo flflflithrouehmloaction zone maintained at a tempornwreiintlie range 650' to 900 C.

11. The method for preparing LS-buisdleiie which consists in passing a. gaseous mixturecomprising one molecular proportion of a. normal butane, from 3 to 45 molecular proportions oi water vapor. from 001 to 0.6 molecular proportions or sul hur dioxide and vfrom 0.01 to Ola chemically equivalent proportions of a hydrogen chloride catalyst at a space velocity oi from 200 to 600 through a reaction zone maintained at a. temperature in the range 050' to 000 C. and recovering 1.3-butadiene from the reacted mixture.

JALIES L. AMOS. FREDERICK J. SODERQUIBT.